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Tumor cells capable of self-renewal and continuous production of progeny cells are called tumor stem cells (TSCs) and are considered to be potential therapeutic targets. However, the mechanisms underlying the survival and function of TSCs are not fully understood. We previously reported that chromatin remodeling regulator Brg1 is essential for intestinal stem cells in mice and Dclk1 is an intestinal TSC marker. In this study, we investigated the role of Brg1 in Dclk1 + intestinal tumor cells for the maintenance of intestinal tumors in mice. Specific ablation of Brg1 in Dclk1 + intestinal tumor cells reduced intestinal tumors in Apc Min mice, and continuous ablation of Brg1 maintained the reduction of intestinal tumors. Lineage tracing in the context of Brg1 ablation in Dclk1 + intestinal tumor cells revealed that Brg1-null Dclk1 + intestinal tumor cells did not give rise to their descendent tumor cells, indicating that Brg1 is essential for the self-renewal of Dclk1 + intestinal tumor cells. Five days after Brg1 ablation, we observed increased apoptosis in Dclk1 + tumor cells. Furthermore, Brg1 was crucial for the stemness of intestinal tumor cells in a spheroid culture system. BRG1 knockdown also impaired cell proliferation and increased apoptosis in human colorectal cancer (CRC) cells. Microarray analysis revealed that apoptosis-related genes were upregulated and stem cell-related genes were downregulated in human CRC cells by BRG1 suppression. Consistently, high BRG1 expression correlated with poor disease-specific survival in human CRC patients. These data indicate that Brg1 plays a crucial role in intestinal TSCs in mice by inhibiting apoptosis and is critical for cell survival and stem cell features in human CRC cells. Thus, BRG1 represents a new therapeutic target for human CRC. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd., (© 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.)

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease. Although rigorous efforts identified the presence of 'cancer stem cells (CSCs)' in PDAC and molecular markers for them, stem cell dynamics in vivo have not been clearly demonstrated. Here we focused on Doublecortin-like kinase 1 (Dclk1), known as a CSC marker of PDAC. Using genetic lineage tracing with a dual-recombinase system and live imaging, we showed that Dclk1 + tumor cells continuously provided progeny cells within pancreatic intraepithelial neoplasia, primary and metastatic PDAC, and PDAC-derived spheroids in vivo and in vitro. Furthermore, genes associated with CSC and epithelial mesenchymal transition were enriched in mouse Dclk1 + and human DCLK1-high PDAC cells. Thus, we provided direct functional evidence for the stem cell activity of Dclk1 + cells in vivo, revealing the essential roles of Dclk1 + cells in expansion of pancreatic neoplasia in all progressive stages., Competing Interests: TM, AF, NG, MT, KI, YH, SO, YN, YY, TY, KT, SU, DS, TC, HS No competing interests declared, (© 2021, Maruno et al.)

Cancer stem cell (CSC)-specific markers may be potential therapeutic targets. We previously identified that Dclk1, a tuft cell marker, marks tumor stem cells (TSCs) in mouse intestinal adenomas. Based on the analysis of mouse Dclk1 + tumor cells, we aimed to identify a CSC-specific cell surface marker in human colorectal cancers (hCRCs) and validate the therapeutic effect of targeting it. IL17RB was distinctively expressed by Dclk1 + mouse intestinal tumor cells. Using Il17rb-CreERT2-IRES-EGFP mice, we show that IL17RB marked intestinal TSCs in an IL13-dependent manner. Tuft cell-like cancer cells were detected in a subset of hCRCs. In these hCRCs, lineage-tracing experiments in CRISPR-Cas9-mediated IL17RB-CreERT2 knockin organoids and xenograft tumors revealed that IL17RB marks CSCs that expand independently of IL-13. We observed up-regulation of POU2F3 , a master regulator of tuft cell differentiation, and autonomous tuft cell-like cancer cell differentiation in the hCRCs. Furthermore, long-term ablation of IL17RB-expressing CSCs strongly suppressed the tumor growth in vivo. These findings reveal insights into a CSC-specific marker IL17RB in a subset of hCRCs, and preclinically validate IL17RB + CSCs as a cancer therapeutic target., Competing Interests: The authors declare no conflict of interest.

Background: Accumulating evidence has shown the existence of tumor stem cells with therapeutic potential. Previously, we reported that doublecortin like kinase 1 (Dclk1) marks tumor stem cells but not normal stem cells in the intestine of Apc Min/+ mice, and that Dclk1- and Lgr5-double positive tumor cells are the tumor stem cells of intestinal tumors., Aim: To investigate molecules highly expressed in the Dclk1 + normal intestinal and Dclk1 + tumor cells in Apc Min/+ mice., Methods: We used microarray analyses to examine the gene expression profile of Dclk1 + cells in both mouse normal intestinal epithelium and Apc Min/+ mouse intestinal tumors. We also performed immunofluorescence analyses., Results: Genes related to microtubules and the actin cytoskeleton (e.g., Rac2), and members of the Src family kinases (i.e., Hck, Lyn, Csk, and Ptpn6) were highly expressed in both Dclk1 + normal intestinal and Dclk1 + tumor cells. Phosphorylated Hck and phosphorylated Lyn were expressed in Lgr5 + cells in the intestinal tumors of Lgr5 EGFP-IRES-CreERT2/+ ; Apc Min/+ mice., Conclusion: We revealed factors that are highly expressed in Dclk1 + intestinal tumor cells, which may help to develop cancer stem cell-targeted therapy in future., (Copyright © 2018 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.)

There is great interest in tumor stem cells (TSCs) as potential therapeutic targets; however, cancer therapies targeting TSCs are limited. A drawback is that TSC markers are often shared by normal stem cells (NSCs); thus, therapies that target these markers may cause severe injury to normal tissues. To identify a potential TSC-specific marker, we focused on doublecortin-like kinase 1 (Dclk1). Dclk1 was reported as a candidate NSC marker in the gut, but recent reports have implicated it as a marker of differentiated cells (for example, Tuft cells). Using lineage-tracing experiments, we show here that Dclk1 does not mark NSCs in the intestine but instead marks TSCs that continuously produce tumor progeny in the polyps of Apc(Min/+) mice. Specific ablation of Dclk1-positive TSCs resulted in a marked regression of polyps without apparent damage to the normal intestine. Our data suggest the potential for developing a therapy for colorectal cancer based on targeting Dclk1-positive TSCs.